<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>返回值 </title>
	<script type="text/javascript">
		
		function abc(num1,num2) {

			if(num1>300){
				return 400;
			}
			return num1+num2;
		}

		var res = abc(400,200);

		document.write(res);


		// res = prompt('你多大了');






	</script>
</head>
<body>
	
</body>
</html>	